Q: A 1000 kg car moves at a constant speed of 20 m/s around a curve of radius 50 m. What is the magnitude of the centripetal force acting on the car?

$$F = m a_{rad} = m \frac{v^2$}{R} = 1000 \times \frac{20^2$}{50} = 8000\ \text{N}$$

Q: A block is pulled by a rope with a force of 10 N at an angle of $$30^\circ$$ above the horizontal. What is the horizontal component of the force?

$$10 \cos 30^\circ = 8.66\ \text{N}$$

Q: A 2 kg object is acted on by a net force of 10 N. What is its acceleration?

$$a = \frac{F}{m} = \frac{10}{2} = 5\ \text{m/s}^2$$

Q: A 5 kg object moves in a circle of radius 2 m at a constant speed of 4 m/s. What is the magnitude of its acceleration?

$$a_{rad} = \frac{v^2$}{R} = \frac{4^2$}{2} = 8\ \text{m/s}^2$$

Q: A block is pulled by a rope with a force of 10 N at an angle of $$30^\circ$$ above the horizontal. What is the vertical component of the force?

$$10 \sin 30^\circ = 5.0\ \text{N}$$

Q: A block of mass 3 kg is acted on by two forces: $$F_1 = 6$$\ \text{N}$$ to the right and F_2$ = 4\ \text{N} to $$the left. What is the acceleration of the block?

$$a = \frac{6 - 4}{3} = 0.67\ \text{m/s}^2 to $$the right

Question 1

A car is moving in a circle at constant speed. Which of the following statements about its acceleration is correct?

Accepted Answer

The acceleration is directed toward the center of the circle and has constant magnitude.

Question 2

A 1000 kg car moves at a constant speed of 20 m/s around a curve of radius 50 m. What is the magnitude of the centripetal force acting on the car?

Accepted Answer

$$F = m a_{rad} = m \frac{v^2$}{R} = 1000 	imes \frac{20^2$}{50} = 8000\ 	ext{N}$$

Question 3

Which of the following best describes the direction of the velocity and acceleration vectors for an object in uniform circular motion?

Accepted Answer

Velocity is tangent to the circle, acceleration is perpendicular to velocity and points toward the center.

Question 4

A battleship fires two shells at ships A and B as shown in the diagram. Both shells are fired simultaneously. Which ship is hit first?

Accepted Answer

Ship A

Question 5

A block is pulled by a rope with a force of 10 N at an angle of $$30^\circ$$ above the horizontal. What is the horizontal component of the force?

Accepted Answer

$$10 \cos 30^\circ = 8.66\ 	ext{N}$$

Question 6

Which of the following is NOT a contact force?

Accepted Answer

Weight (gravitational force)

Question 7

A puck on a frictionless surface is acted on by two horizontal forces of equal magnitude but opposite direction. What is the net force and acceleration on the puck?

Accepted Answer

Net force is zero, acceleration is zero.

Question 8

A 2 kg object is acted on by a net force of 10 N. What is its acceleration?

Accepted Answer

$$a = \frac{F}{m} = \frac{10}{2} = 5\ 	ext{m/s}^2$$

Question 9

Which of the following statements about Newton’s third law is correct?

Accepted Answer

The action and reaction forces are equal in magnitude and opposite in direction.

Question 10

A block rests on a horizontal surface. Which force is responsible for supporting the block against gravity?

Accepted Answer

Normal force

Question 11

A child is pulled on a sled across snow. If the sled moves at constant velocity, what can you say about the net force acting on the sled?

Accepted Answer

The net force is zero.

Question 12

A 5 kg object moves in a circle of radius 2 m at a constant speed of 4 m/s. What is the magnitude of its acceleration?

Accepted Answer

$$a_{rad} = \frac{v^2$}{R} = \frac{4^2$}{2} = 8\ 	ext{m/s}^2$$

Question 13

Which of the following is the correct SI unit for force?

Accepted Answer

Newton (N)

Question 14

A block is pulled by a rope with a force of 10 N at an angle of $$30^\circ$$ above the horizontal. What is the vertical component of the force?

Accepted Answer

$$10 \sin 30^\circ = 5.0\ 	ext{N}$$

Question 15

A block of mass 3 kg is acted on by two forces: $$F_1 = 6$$\ 	ext{N}$$ to the right and F_2$ = 4\ 	ext{N} to $$the left. What is the acceleration of the block?

Accepted Answer

$$a = \frac{6 - 4}{3} = 0.67\ 	ext{m/s}^2 to $$the right

Question 16

Which of the following best describes the effect of the component of acceleration parallel to velocity in non-uniform circular motion?

Accepted Answer

It changes the speed of the object.

Question 17

A block is at rest on an inclined plane. Which force prevents it from sliding down?

Accepted Answer

Friction force

Question 18

A carnival ride moves in a circle of radius $$5.0\ 	ext{m}$$ and completes one revolution in $$4.0\ 	ext{s}. $$What is the magnitude of the acceleration of the passengers?

Accepted Answer

$$a_{rad} = \frac{4\pi^2$ R}{T^2$} = \frac{4 	imes \pi^2$ 	imes 5.0}{16} \approx 12.3\ 	ext{m/s}^2$$

Motion in a Plane and Newton's Laws of Motion: Study Notes

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드